The genetic basis behind the evolution of bone fusion (co-ossification) in birds has remained unexplored. Bone morphogenic proteins (BMPs), especially BMP2 and BMP4, are well known for their integral role in skeletal ossification during embryogenesis in vertebrates. This project will use comparative genomics to clarify osteogenic bmp2 and bmp4 evolution in birds and reptiles as they relate to the evolution of skeletal co-ossification on the phylogenetic line to birds. Three primary aims are designed to address this problem. Aim one is to "sequence bmp2 and bmp4 from BAG libraries in several birds, a crocodilian, and several saurian outgoups. I will accomplish this in Scott Edwards' laboratory at Harvard's Department of Organismic and Evolutionary Biology and Museum of Comparative Zoology, which already possesses the BAG libraries and equipment required for this project. Aim two is to elucidate the evolution of bmp2 and bmp4 regulatory regions. Aim three is to elucidate the evolution of bmp2 and bmp4 coding regions. This project will be the first large scale examination of non-avian reptile genome structure and evolution.